key performance indicators for the uk national dairy herd

Key Performance Indicators for the UK national dairy herd

A study of herd performance in 500 Holstein/Friesian herds for the year

ending 31st August 2020

Dr. James Hanks &

Dr. Mohamad Kossaibati

November, 2020

Veterinary Epidemiology & Economics Research Unit (VEERU), School of Agriculture Policy & Development,

University of Reading, P.O.Box 237

Reading, RG6 6AR

[email protected]

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Table of Contents

Executive Summary .............................................................................................................. 1

Section 1: Description of the study and methods used ..................................................... 3 Introduction .......................................................................................................................................... 3 Parameter description ........................................................................................................................... 3 The sample of herds ............................................................................................................................. 3 The parameters ..................................................................................................................................... 4 Changes to studies from earlier years .................................................................................................. 5 Acknowledgements .............................................................................................................................. 6

Section 2: KPI results for the year ending 31 August 2020 ............................................. 7

Section 3: Trends in Key Performance Indicators 2010 to 2020 .................................. 27 Changes in Herd size over the 11 annual KPI studies ....................................................................... 28 Changes in Key Parameters over the 11 annual KPI studies ............................................................. 28

Section 4. The Practical Use of Key Performance Indicators By Farmers And Their Technical Advisers ......................................................... 38

Using the target and range values to highlight a herd’s strengths & weaknesses .............................. 40 Relationship between parameters: Herd SCC vs % chronic high SCC milk samples ....................... 41

Appendix 1. Changes in Key Performance Indicators between 2010 and 2020 in herds included in every study over 11 years .............................. 43

Appendix 2. Key Performance Indicators definitions ................................................. 44

Appendix 3. Herd Companion High SCC Categories.................................................. 47

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Executive Summary This is the eleventh annual study of Key Performance Indicators (KPI) from a cross-section of 500 dairy herds that milk record with National Milk Records (NMR). Starting in 2010, each study covers over 70 different parameters describing aspects of fertility, production and health. The principal objective of the studies is to provide farmers and their technical advisers with accurate and current descriptions of performance levels as the basis for discussion and target setting at herd level. The method of calculation for the majority of the 38 parameters described in this study is identical in all studies. Consequently the studies provide both a description of current performance of the national dairy herd and how this has changed over the 11 year period. For each parameter the 500 herds are arranged in ascending/descending order. The median is then the average of the middle two herds (herds in position 250 and 251). It follows that 50% of herds fall above and 50% of herds fall below this median value. Herd size: Herd sizes have remained relatively stable for the last four years.

• Median herd size in 2020 is 174 cows. One herd in four has more than 252 cows and one herd in four has less than 118 cows.

• While the median herd size has increased by 45cows since 2010, the herd sizes have not changed markedly in the last 4 years.

Longevity: Longevity and culling rates have also remained at similar levels in the last four years • The median age at first calving in 2020 is 2.3 years, unchanged since 2015. • The median age at exit is 6.0 years giving 3.7 years of productive life. While lower than in

2010this is unchanged since 2017. • The median lactations per cow at exit for 2020 is 3.5 lactations. While 0.4 lactations less than

in 2010 this has remained relatively constant since 2016. • The median culling rate in 2020 is 28%. While 4% higher than in 2010 this has remained

relatively constant since 2016.

Fertility: While conception rates are largely unchanged, heat detection continues to improve • The median calving interval in 2020 is 400 days. This has remained at a similar level since

2018 following a steady reduction from 424 days in 2010. • The median conception rate in 2020 is unchanged since 2018 at 35%. There remains a

wide variation in conception rate between herds. One herd in four has a conception rate of 29% or less, a figure that is also unchanged since 2018.

• Heat detection: The steady improvement in heat detection since 2010 continues. The median % of inter-service intervals at 18-24 days (the 1st available oestrus after a failure to conceive) in 2020 is 39%, an improvement of 9% compared to 30% in 2010. The median herd % of intervals that are greater than 50 days (suggesting 2+ missed oestrus cycles) is 21%, an improvement of 11% compared to 32% in 2010. However, one herd in four still detects under 31% of service returns at the first available oestrus. Similarly, in a quarter of herds over 28% of inter-service intervals still exceed 50 days.

• The median submission rate in 2020 is 40%. While this is a 13% increase compared to 27% in 2010 this is only a 2% improvement compared to 38% in 2016.

• The median pregnancy rate in 2020 is 14%. While this has increased from 9% in 2010 it has remained relatively unchanged since 2017.

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• The median % cows served by day 80 (after calving) in 2020 is 60%. This is 14% higher than 46% in 2010 with most improvement occurring before 2014. In 2020 one herd in four served less than 47% of cows at least once by day 80 after calving.

• The median % conceived by day 100 (after calving) in 2020 is 36%. This is 10% higher than 26% in 2010 although there has been relatively little change since 2017.

Milk production: Production per cow per year continues to increase with a slight fall in lifetime daily yield. There is a marked increase in fat% of milk recorded in 2020

• The median Lifetime milk per cow per day (since birth) in 2020 is 12.8kg (slightly less than that in 2019 – 13.0kg). The top quartile of herds has increased every year since 2013.

• The median Milk per cow per year (milk per cow place) in 2020 is 8,904kg. This is the seventh consecutive annual increase, up by 167kg since the 2019 study. Since 2010 the median milk/cow/year has increased by 16% (1,239kg).

• The median protein % content of milk at 3.32% in 2020 has remained similar to 2019 following gradual increases in recent years.

• The median fat % content of milk is 4.13% in 2020. While this has risen from 3.96% in 2010, the majority of the increase was in 2020 (0.11% increase from 4.02% from 2019). The fat kg yield per cow per year in 2020 is an increase of 16.51 kg (4.7%) over 2019.

Somatic Cell Counts (SCC): The significant improvements in recent years are maintained. In half the herds nearly half the cows now complete lactations without recording any high SCC

• The median herd SCC in 2020 is almost unchanged at 173,000 cells / ml milk. The median herd SCC has declined by 37,000 cells/ml milk since 2010. The median herd SCC in 2010 (210,000) was bettered by 357/500 (71%) of herds in 2020.

• 328 (66%) of the 500 herds had a herd SCC below 200,000 cells in 2020. This contrasts with 218/500 (44%) herds in the 2010 study.

• The median level of chronic high SCC cows in 2020 is 8%. There has been a consistent improvement (decline) from 14% in 2010. The strong association (R2>0.7) between the %chronic high SCC cows and herd SCC occurred in every study. In 2020, 52/500 (about 10%) herds recorded over 15% chronic cows, down from 207 (41%) in the original 2010 study. In 2020, 325/500 (65%) herds recorded less than 10% chronic cows, up from 121 (24%) in 2010 (see 4).

• The median % cows completing lactations with no high SCC recordings in 2020 is 49%. So in half the herds, half the cows (49%) completed lactations without recording a single high SCC. The equivalent in 2010 was a third of cows (33%) completing lactations without recording a single high SCC.

Mastitis: Cases are not consistently recorded across all 500 herds. Since 2016 a subset of the 500 herds (recording 5 or more cases/100 cows/year) has been included for analysis of mastitis incidence.

• Mastitis incidence in the median herd of the 2020 subset is 28 cases per 100 cows per year, a reduction of 8 cases per 100 cows per year from 2016.

• In half the herds (with mastitis records) 81% of cows recorded no mastitis in the lactation, an increase from 79% in 2016.

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Section 1: Description of the study and methods used

Introduction This is the 11th annual study describing key indicators of production, fertility and health in commercial black and white dairy herds in the United Kingdom. The Key Performance Indicators (KPIs) are based on milk recording data from 500 commercial black and white herds for the 12 month period ending on 31st August 2020. Herd selection used random numbers to ensure a representative cross-section of all herds (good, bad and indifferent) that milk record with National Milk Records (NMR). The range in performance across these herds is described for 38 parameters clearly showing the wide differences in performance, as well as huge potential for improvement, in commercial dairy herds. This includes six additional parameters (including mastitis rate/100 cows in milk/year) shown since the 2016 study. The principal objective throughout has been to provide farmers and technical advisers with accurate and up-to-date information on the variation in performance of commercial dairy herds. The calculations used to generate these parameters are identical to those used by the InterHerd+ program allowing farmers and technical advisers to compare the performance of any milk recording herd directly with the 500 herd sample that is representative of the national performance. In other words, for each parameter: “Is the performance of my herd typical/outlying, good/acceptable/poor when compared to the 500 herds?”. This prompts discussion around: “Why is a parameter where it is? Which parameters could/should we prioritise/improve and what are the likely implications?” If this promotes discussion between farmers and their technical advisers into the different causes and options for improvement then the study has served its primary purpose. Following the analysis of individual parameters there is a section on trends since 2010 for a selection of the KPIs. Further sections discuss their practical use by farmers and advisers. A KPI template of 80 parameters for use in InterHerd+ is also available for users to update the KPI parameters to the target values from the 2020 study.

Parameter description For 35 parameters described in this study (out of total of 38), the performance level of each of the 500 herds (255 herds for mastitis rate) is presented as a bar chart. The herds are displayed from “best” to “worst”, in ascending or descending order depending on whether it is generally preferable to have a low value (e.g. SCC, calving interval) or a high value (e.g. dry period cure, conception rate). The “best” is always on the left side, nearest the vertical Y axis. For each parameter, a median (middle) value and inter-quartile range values (the level achieved by the middle 50% of herds) are also derived. The target value proposed for each parameter (and included in the KPI template) is the level achieved by the “best” 25% of the herds for that parameter. In other words, the target is set at a level that is currently achieved (or exceeded) by one in four dairy herds over the last year.

The sample of herds The source of data is the monthly milk records obtained by National Milk Records (NMR). The 500 herds used in the study all fully milk record on a monthly assisted basis and are approximately 10% of herds recorded by NMR. Herds were selected using random numbers to ensure a representative cross-section of the sample. The herds are all predominantly comprised of black and white breeds (Holstein, Holstein-Friesian, Friesian) and have recorded for a minimum of two years. Where possible the same herds used in the 2019 study were maintained for the 2020 herds’ sample. Herds with poorly recorded fertility data (inadequate recording of services and pregnancy diagnoses), as well as herds no longer recording, were replaced with new herds, again selected using random numbers. In total 436 herds (87%) were in both the 2019 and 2020 studies.

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Herd size for the 500 herds in the 2020 study ranged from minimum 45 to maximum 889 cows, with a median value of 174 cows, as shown in Figure 1. In the sample 60% of herds were comprised of less than 200 cows, with 38 herds containing over 400 cows. Figure 1. Herd size of the 500 herds in the 2020 study

The parameters To minimize the impact of short term seasonal variations, the key performance indicator values are calculated using data recorded over a full 12 month period. They represent the consolidated or average performance levels achieved by each herd for the period from 01 September 2019 to 31 August 2020. The definitions of each parameter are detailed in Appendix 1. The results of the study are summarized in Tables 1(a) & 1(b). For each parameter, four statistics are presented:

1. The median: The middle value. If the performance levels of all herds are arranged in ascending order, the median is the performance of the middle herd (or the average of the middle two herds in an even number of herds). Half the herds do better and half do worse than the median value.

2. The first quartile (25% value) and third quartile (75% value). With the median, these split the herds into four equal groups. The first and third quartile values are the lower and upper limits of performance achieved by the middle 50% of herds. 25% achieve “better” and 25% achieve “worse” than the limits for that parameter.

3. The target value used by InterHerd+ is the level achieved or bettered by 25% of the herds in the study. This value is the “better” of the first quartile (25%) or third quartile (75%) values. For parameters like somatic cell count, culling % and calving interval the target will be the 25% (lower) value, while for others (conception %, protein %, dry period cure %) it will be the 75% (higher) value.

4. The inter-quartile range is the difference between the performance of the best and worst 25% of herds (i.e. the difference between the first quartile (25% value) and third quartile (75% value). This gives an impression of how widely herds in the middle 50% differ.

The position of these values is graphically displayed in Figure 2. Throughout this report the parameter value is displayed on the vertical Y axis and bars representing the study herds are arranged along the horizontal X axis. The “best” performing herd is nearest the vertical Y axis with the worst performing herd furthest away.

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The parameter described in Figure 2 is the herd average SCC so the target value is at the lower end of the inter-quartile range (as a low average SCC is preferable to a high average SCC). Figure 2. A description of the median, inter-quartile range and target values generated for each parameter

Changes to studies from earlier years 1. Mastitis Key Performance Indicators: The results of the study summarized in Tables 1(a) &

1(b) include 4 parameters relating to mastitis, including the herd overall Mastitis rate (cases/100 cows in milk/year). This is the fifth year that mastitis related parameters have been derived from the survey herds, reflecting the significant improvement in the level of reporting of mastitis by farmers in recent years. While in 2012 less than 20% of herds reported any mastitis, this has risen to over 51% of herds in 2020. For the purpose of this study any herd that recorded over 5 cases/100 cows in milk/ year was considered to record mastitis. The mastitis KPIs in this report are calculated based on 255 of the 500 herds (51%) that qualified this year.

2. 305 day milk/protein/fat yields: In previous reports up to that of 2015, 305 day yield

parameters were calculated from all lactations, including lactations that were shorter than 305 days. In this report, as in all years since 2016, the lactation must be at least 305 days long for inclusion in the calculation. This report also details the 305 day yields (total yield up to and including the 305th day of lactation) of fat and protein. As with the milk yield, these parameters are calculated from lactations that were at least 305 days in length. Note that the exclusion of lactations shorter than 305 days does not apply to the calculation of the overall lactation yield. In some herds, when many cows have lactation lengths below 305 days, this can result in lactation yields smaller than the 305 day yields.

3. For the last 2 years, the report presented new ‘KPIs’ related to the sero-prevalence of Johne’s

disease, based on results from a sub-group of herds from the 500 herds which have been regularly (quarterly) ‘whole herd’ tested using the milk ELISA over at least the previous 2 years. However, this year the Johne’s KPIs will be shown in a separate report on completion of a detailed study of Johne’s disease across the current NMR 500 herds.

25% value (Target) 75% value Median

(mid-value)

Inter-quartile range (25% - 75%)

Herds achieving better than target

(top 25%)

Herds in the “worst” 25%

nationally

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Acknowledgements The authors are very grateful to National Milk Records (NMR) for their assistance and cooperation with the preparation of this study. The authors also acknowledge the contribution of VEERU colleagues Kulwant Channa for his technical support, and Nick Taylor in the final proof-reading, technical support and editing.

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Section 2: KPI results for the year ending 31 August 2020 Table 1(a) Summary of Key Performance Indicators derived from analysis of 500 NMR milk recording herds for the year ending 31 August 2020 – Culling, fertility & milk parameters.

Parameter Median

(1)

1st - 3rd quartile (25% - 75%)

(2) Target

(3)

Inter-quartile range

(4) A. Culling rate 28% 23% - 34% 23% 11%

B. Percentage culled (off take) 100 days after calving 5% 3% - 7% 3% 4%

C. Age at exit (years) 6.0 5.4 - 6.6 6.6 1.2

D. Age at exit by lactations 3.5 3.1 - 4.0 4.0 0.9

E. Percentage Served by day 80 60% 47% - 70% 70% 23%

F. Percentage conceived 100 days after calving 36% 27% - 42% 42% 15%

G. Calving to 1st service interval (days) 80 70 - 95 70 25

H. Calving interval (days) 400 388 - 417 388 29

I. Age at 1st calving (years) 2.3 2.1 - 2.5 2.1 0.4

J. Conception rate 35% 29% - 41% 41% 12%

K. %Service intervals at 18-24 days (Heat detection) 39% 31% - 45% 45% 14%

L. Percentage service intervals >50 days 21% 14% - 28% 14% 14%

M. %Cows eligible for service served (Submission rate) 40% 28% - 51% 51% 23%

N. %Eligible for service that conceived (Pregnancy rate) 14% 10% - 18% 18% 8%

O. Lifetime milk / cow / day (kg) 12.8 10.9 - 15.1 15.1 4.2

P. Milk / cow / year (kg) 8,904 7,700 - 9850 9,850 2,150

Q. Average protein% 3.32% 3.26% - 3.40% 3.40% 0.14%

R. Average fat% 4.13% 3.94% - 4.29% 4.29% 0.35%

S. 305-day milk yield (kg) 9,255 8,130 - 10,249 10,249 2,119

T. 305-day protein yield (kg) 307 270 - 337 337 67

U. 305-day fat yield (kg) 378 331 - 416 416 85

(1) The median is the middle value (so 250 herds were better and 250 were worse than this value). (2) The first quartile (25% value) and third quartile (75% value) describe the lower and upper limits of

performance achieved by the middle 50% of herds. 25%, or one in four, herds achieve “better” and 25% “worse” than the limits for that parameter.

(3) The Target is set at the level achieved or bettered by the “best” 25% of herds. One in four of the 500 herds in the sample achieved this level or better.

(4) The inter-quartile range is the difference between the first quartile (25% value) and third quartile (75% value). This gives an impression of how widely herds in the middle 50% differ.

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Table 1(b) Summary of Key Performance Indicators derived from analysis of 500 NMR milk recording herds for the year ending 31 August 2020 – Somatic Cell Count (SCC) and mastitis parameters.

Parameter Median

(1)

1st - 3rd quartile (25% - 75%)

(2) Target

(3)

Inter-quartile range

(4) V. Herd SCC (‘000 cells/ml) 173 138 - 217 138 79 W. % milk samples with High SCC (*) 17% 13% - 21% 13% 8% X. % milk samples with SCC ≥500,000 cells/ml 7% 5% - 9% 5% 4% Y. % cows with High SCC at 1st record in lactation (*) 16% 12% - 21% 12% 9% Z. % Chronic milk samples (**) 8% 6% - 11% 6% 5% ZA. Dry period cure (High:Low) (***) 76% 69% - 84% 84% 15% ZB. Dry period protection (Low:Low) (***) 85% 80% - 89% 89% 9% ZC. % Low at last recording of previous lactation (*) 76% 68% - 83% 83% 15% ZD. % samples New SCC category (**) 6% 5% - 8% 5% 3% ZE. % cows dried-off with no High SCC samples in the lactation (*) 49% 41% - 57% 57% 16%

ZF. Threshold Index new high / new low (****) 1.26 1.13 - 1.40 1.13 0.27 ZG. % of cows with New/First/Repeat sample that are Low SCC at next recording (**) 54% 50% - 60% 60% 10% ZH. % of cows with Chronic sample that are low SCC at next recording (**) 21% 17% - 26% 26% 9%

ZI. Percentage drying off with no mastitis cases+ 81% 74% - 88% 88% 14% ZG. Mastitis rate (cases/100 cows in milk/year)+ 28 18 - 44 18 26 ZK. Cows with Index mastitis case by Day 30+ 5% 2% - 7% 2% 5% ZL. Index mastitis rate after Day 30+ 19% 12% - 28% 12% 16%

(*) HIGH SCC is a milk sample with ≥200,000 cells/ml milk; LOW SCC is a milk sample with below 200,000 cells/ml milk

(**) CHRONIC / NEW / FIRST and REPEAT are the Herd Companion categories describing high SCC cows. See Appendix 2 for definitions.

(***) Dry period protection (High:Low): The percentage of cows finishing a lactation with a HIGH SCC sample that starts the new lactation with a LOW SCC sample; Dry period cure (Low:Low): The percentage of cows finishing a lactation with a LOW SCC sample that starts the new lactation with a LOW SCC sample.

(****) Threshold Index: The total cows changing from Low to High SCC divided by the total cows changing from High to Low SCC at consecutive milk recordings.

(1) The median is the middle value (so 250 herds were better and 250 were worse than this value). (2) The first quartile (25% value) and third quartile (75% value) describe the lower and upper limits of

performance achieved by the middle 50% of herds. 25%, or one in four, herds achieve “better” and 25% “worse” than the limits for that parameter.

(3) The Target is set at the level achieved or bettered by the “best” 25% of herds. One in four of the 500 herds in the sample achieved this level or better.

(4) The inter-quartile range is the difference between the first quartile (25% value) and third quartile (75% value). This gives an impression of how widely herds in the middle 50% differ.

+ The mastitis parameters are derived from a group of 255 herds (within the 500 herds in the study) where mastitis rate >5 cases per 100 cows in milk / year.

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A. Culling/death rate: The % of cows that left the herd (culled/sold/died) in the last 12 months. Target (top ¼ of herds’ level): 23%

Median: 28% 75% level: 34%

Inter-quartile range: 11%

B. Percentage of cows/heifers calving during the last 12 months that were culled (off take) / died

during the first 100 days after calving. A possible indicator of “involuntary culling”. Target (top ¼ of herds’ level): 3%



“Target” ≤ 23%

“Worst ¼ of the herds” >34%

“Target” ≤ 3%

“Worst ¼ of the herds” >7%

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C. Average Age (in years) at exit: The average age of cows leaving the herd in the last 12 months at the time of exit. A potential measure of longevity.

Target (top ¼ of herds’ level): 6.6 Median: 6.0

75% level: 5.4 Inter-quartile range: 1.2

D. Average Age at exit by lactations: The average lactation number of cows leaving the herd in

the last 12 months. A potential measure of longevity. Target (top ¼ of herds’ level): 4.0

Median: 3.5 75% level: 3.1

Inter-quartile range: 0.9

“Worst ¼ of the herds” < 5.4

“Target” > 6.6

“Target” > 4.0


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E. % Served by day 80: The percentage of calving cows served at least once within 80 days of calving.

Target (top ¼ of herds’ level): 70% Median: 60%

75% level: 47% Inter-quartile range: 23%

F. % conceived 100 days after calving: The percentage of calving cows that had conceived within

100 days of calving. Target (top ¼ of herds’ level): 42%



“Worst ¼ of the herds” < 27%


“Target” > 70%

“Target” > 42%

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G. Calving to 1st service interval: The average number of days between calving and 1st service. Target (top ¼ of herds’ level): 70

Median: 80 75% level: 95

Inter-quartile range: 25

H. Calving interval: The average interval between consecutive calvings (in days).

Target (top ¼ of herds’ level): 388 Median: 400

75% level: 417 Inter-quartile range: 29

“Target” < 388

“Worst ¼ of the herds” > 417

“Target” < 70


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I. Age at 1st calving: The average age (in years) of heifers calving down over the last year. Target (top ¼ of herds’ level): 2.1

Median: 2.3 75% level: 2.5


J. Conception rate: The average conception rate for all services in the last 12 months.



“Worst ¼ of the herds” > 2.5

“Target” > 41%

“Target” < 2.1


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K. % service intervals at 18-24 days (Heat detection): The percentage of all repeat services occurring 18-24 days (one oestrous cycle) after the previous service.



L. % service intervals >50 days: The percentage of all repeat services with an interval of over 50

days since the previous service. A potential indicator of poor heat detection. Target (top ¼ of herds’ level): 14%



“Target” < 14%

“Worst ¼ of the herds” > 28%

“Target” > 45% “Worst ¼ of the herds”

< 31%

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M. Percentage of cows eligible for service (>42 days calved, not barren, not pregnant) that were served per 21 day oestrous period (Submission rate).



N. Percentage eligible for service (>42 days calved, not barren, not pregnant) that conceived per

21 day oestrus period (Pregnancy rate). Target (top ¼ of herds’ level): 18%




“Target” > 18%

“Target” > 51%


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O. Lifetime milk / cow / day (kg): Equates to the average daily milk yield of cows across their whole lifetime (including unproductive periods: time as a heifer, dry periods).

Target (top ¼ of herds’ level): 15.1 Median: 12.8

75% level: 10.9 Inter-quartile range: 4.2

P. Milk / cow / year (kg): The average annual milk yield of all cows in the year. Total milk

divided by the average cow population. A measure of milk yield per cow place in the herd. Target (top ¼ of herds’ level): 9,850

Median: 8,904 75% level: 7,700

Inter-quartile range: 2,150

“Target” > 9,850

“Target” > 15.1

“Worst ¼ of the herds” < 7,700


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Q. Average protein (%): The average % protein of all milk samples taken over the year. Target (top ¼ of herds’ level): 3.40%

Median: 3.32% 75% level: 3.26%

Inter-quartile range: 0.14%

R. Average fat (%): The average % fat of all milk samples taken over the year.

Target (top ¼ of herds’ level): 4.29 % Median: 4.13%

75% level: 3.94% Inter-quartile range: 0.35%

“Target” > 3.40%

“Worst ¼ of the herds” < 3.26%

“Target” > 4.29% “Worst ¼ of the herds”

< 3.94%

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S. 305 day yield (kg): The average yield of cows by day 305 of the lactation. Target (top ¼ of herds’ level): 10,249

Median: 9,255 75% level: 8,130

Inter-quartile range: 2,119

T. 305 day protein (kg): The average milk protein yield of cows by day 305 of the lactation.

Target (top ¼ of herds’ level): 337 Median: 307

75% level: 270 Inter-quartile range: 67

“Target” > 10,249 “Worst ¼ of the herds”

< 8,130

“Target” > 337 “Worst ¼ of the herds”

< 270

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U. 305 day fat (kg): The average milk fat yield of cows by day 305 of the lactation. Target (top ¼ of herds’ level): 416



V. Herd SCC (‘000 cells/ml): The weighted average SCC of all milk samples taken in the last 12

months (weighted for volume of production of each cow producing the sample). Target (top ¼ of herds’ level): 138



“Target” > 416 “Worst ¼ of the herds”

< 331

“Target” < 138


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W. % of milk samples with high SCC: The percentage of milk samples in the last 12 months with a SCC ≥ 200,000 cells/ml of milk. Indicates the size of any reservoir of infection.



X. % of milk samples with SCC ≥ 500,000 cells/ml: The percentage of milk samples taken in the

last 12 months with a SCC ≥ 500,000 cells/ml of milk. Target (top ¼ of herds’ level): 5%



“Target” < 13%



“Target” < 5%

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Y. % 1st recording SCC ≥ 200,000 cells/ml: The percentage of new lactations in the last year starting with a high SCC (≥ 200,000 cells) at the first milk recording.



Z. Percentage chronic SCC ≥ 200,000 cells/ml: The % of all milk samples taken over the last 12

months that were from CHRONIC cows (cows whose milk was ≥ 200,000 cells at both the CURRENT AND PREVIOUS milk recordings).



“Target” < 12%


“Target” < 6%


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ZA. Dry period cure (High:Low): The % of cows calving in the last year that ended their previous lactation with a high SCC (≥ 200,000 cells), started the new lactation with a LOW cell count (< 200,000 cells). The % of high SCC cows “cured” in the dry period.



ZB. Dry period protection (Low:Low): The % of cows calving in the last year that ended the

previous lactation with a LOW SCC (< 200,000 cells) then started the new lactation with a LOW cell count (< 200,000 cells). The % of low SCC cows “protected” in the dry period.




< 69%


< 80%

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ZC. % Low at the end of previous lactation: The percentage of cows calving in the last year that ended their previous lactation with a LOW SCC (< 200,000 cells).



ZD. % NEW SCC milk samples: Of all milk samples, the percentage that were of the NEW Herd

Companion SCC Category (the first HIGH SCC (≥ 200,000cells/ml) in a lactation following one or more low SCC samples).




< 68%

“Target” < 5%


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ZE. % dried-off with no SCC ≥ 200,000 cells/ml: The percentage of cows recording only LOW SCC samples (< 200,000 cells/ml) in completed lactations.



ZF. Threshold Index new high / new low: The total cows changing from Low to High SCC

divided by the total cows changing from High to Low SCC at consecutive recordings. Target (top ¼ of herds’ level): 1.13

Median: 1.26 75% level: 1.40


“Target” > 57%


“Target” < 1.13

“Worst ¼ of the herds” > 1.40

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ZG. Recovery % of New/First/Repeat infections: Of HIGH SCC cows (≥ 200,000cells/ml) that at the previous recording were either low SCC or not yet in milk, the percentage that were LOW SCC (< 200,000 cells/ml) at the following recording.



ZH. Recovery % of chronic infections: Of cows with two or more consecutive HIGH SCC

recordings (≥ 200,000 cells/ml), the percentage that recorded a LOW SCC (< 200,000 cells/ml) at the following recording.




< 50%

“Target” > 26%


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ZJ. Mastitis rate: Number of clinical mastitis cases per 100 cows in milk in the herd over a year. Target (top ¼ of herds’ level): 18



“Target” < 18


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Section 3: Trends in Key Performance Indicators 2010 to 2020 The target and median figures from the current study are compared with the results from the first study for the year ending 30 September 2010 and from last year’s study. Table 2 below shows changes in the median and target (top 25% performance) values for each parameter over the period. The majority of parameters have improved (green) over the period with the exception of overall culling, age & number of lactations at exit which show some deterioration (red). Some of the parameters have continued to improve since last year (2019), while some others have remained the same (black, in the 2020 columns). There is no attempt at identifying any statistical significance in these changes. Higher culling rate, and hence lower number of lactations at exist, remain in the same negative trend.

Table 2. Comparison of median and target values derived from the study of 500 NMR recording herds in 2019 with the original study in 2010, and with the current results as well.

Parameter Median Target “Best 25%” Year of the Study 2010 2019 2020 2010 2019 2020

A. Culling rate 24% 27% 28% 18% 22% 23% B. Percentage culled (off take) / died 100 days after calving 7% 5% 5% 4% 3% 3%

C. Age at exit (years) 6.6 6.0 6.0 7.4 6.7 6.6 D. Age at exit by lactations 3.9 3.6 3.5 4.5 4.0 4.0 E. Percentage Served by day 80 46% 58% 60% 59% 68% 70% F. Percentage conceived 100 days after calving 26% 34% 36% 33% 41% 42% G. Calving to 1st service interval (days) 105 81 80 87 71 70

H. Calving interval (days) 424 401 400 409 387 388 I. Age at 1st calving (years) 2.4 2.3 2.3 2.3 2.1 2.1 J. Conception rate 32% 35% 35% 40% 42% 41% K. %Service intervals at 18-24 days (Heat detection) 30% 37% 39% 38% 44% 45%

L. %Service intervals >50 days 32% 21% 21% 22% 15% 14% M. %Cows eligible for service served (Submission rate) 27% 39% 40% 37% 51% 51% N. %Cows eligible for service conceived (Pregnancy rate) 9% 14% 14% 13% 18% 18%

O. Lifetime milk / cow / day (kg) 10.5 13.0 12.8 12.6 14.9 15.1 P. Milk / cow / year (kg) 7,665 8,737 8,904 8,760 9,761 9,850 Q. Average protein% 3.27% 3.32% 3.32% 3.33% 3.39% 3.40% R. Average fat% 3.96% 4.02% 4.13% 4.12% 4.17% 4.29% V. Average SCC (‘000 cells/ml) 210 171 173 169 136 138 W. % SCC ≥200,000 cells/ml 24% 17% 17% 19% 13% 13% X. % SCC ≥500,000 cells/ml 9% 7% 7% 7% 5% 5% Y. % 1st recording SCC ≥200,000 cells/ml 20% 16% 16% 15% 12% 12%

Z. % chronic SCC ≥200,000 cells/ml 14% 9% 8% 10% 6% 6% ZA. % Dry period cure (High:Low) 74% 77% 76% 80% 85% 84% ZB. % Dry period protection (Low:Low) 84% 85% 85% 89% 90% 89% ZC. % Low at end of previous lactation (SCC<200,000 cells/ml) 60% 74% 76% 70% 81% 83%

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Changes in Herd size over the 11 annual KPI studies Figure 3 below shows changes in herd size (number of cows) since 2010, indicating dairy herds in UK tended to increase in size over the last 11 years with a large range between the larger and the smaller 25% of the herds. Figure 3. Herd size

Changes in Key Parameters over the 11 annual KPI studies The figures below show the changes over the ten annual KPI studies (2010 to 2020) for a number of important parameters. The three lines represent the “better” quartile, median and “poorer” quartile values each year for each parameter. 3.1 Trends in Culling & Longevity Parameters over the last 11 years

Figure 4. Culling rate

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Figure 5. Culling (off take) / died in the first 100 days of lactation

Figure 6. Age at exit (by number of Years)

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Figure 7. Age at exit (by number of Lactations)

3.2 Trends in Key Fertility Parameters over the last 11 years Figure 8. Age at first calving

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Figure 9. Percentage of cows served by Day 80 after calving

Figure 10. Percentage of cows pregnant (conceived) by Day 100 after calving

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Figure 11. Percentage of all repeat services that are 18-24 days after the previous service (Heat detection)

Figure 12. Percentage of all service resulting in a conception

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Figure 13. Submission rate

Figure 14. Pregnancy rate

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Figure 15. Calving interval

3.3 Trends in Milk Production Parameters over the last 11 years Figure 16. Lifetime milk per cow / day (kg). This includes days between birth and first calving.

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Figure 17. Milk per cow / year (kg)

3.4 Trends in Key SCC (over last 11 years) & Mastitis Parameters (over the last 5 years) Figure 18. Herd Somatic cell Count

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Figure 19. Percentage of milk samples originating from chronic (repeat) high SCC cows

Figure 20. Percentage of cows dried-off with no high SCC in lactation

% Dried -off with no SCC ≥ 200,000 cells/ml (500 NMR Herds – Trends over 11 years)

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Figure 21(a). Mastitis rate (cases / 100 cows in milk / year) – mastitis groups of herds in last 5 years

Figure 21(b). Mastitis rate (cases / 100 cows in milk / year) – the same herds over last 5 years

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Section 4. The Practical Use of Key Performance Indicators By Farmers And Their Technical Advisers The figures obtained from this study can be treated as “national standards” for UK 'black and white' dairy herds in 2020, with target values set at the level currently achieved or bettered on one in four of the 500 farms in the survey. A farmer can readily see where their herd would perform for each parameter relative to the 500 herds. This can be used to focus discussion on the causes and options/need for improvement. The Key Performance Indicators Report in the InterHerd+ program provides an overview of performance for an individual herd. Parameters are calculated in an identical way so are directly comparable to the KPI values in the study. Comparing the performance of the herd with the results of the study highlights areas of strength and weakness in that herd’s performance (Figure 22). The combination of parameters relating to production, fertility and health, emphasizes the dynamic nature of dairy production and the need for high standards across all areas of herd management. Many herds are excellent in one area of production, fertility or health but seldom in all. There is always room for improvement in efficiency. Figure 22. The Key Performance Indicator Report of InterHerd+

Better than target (top 25%

nationally)

Lowest 25%

nationally

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The meaning of the different lines and values against each key performance indicator are explained in Figure 23 below. Figure 23. The KPI Report: The figures explained

The value displayed to the left of each parameter title represents the herd’s performance over the last year. It is the rolling 12 month average for that parameter. In Figure 23 the herd had a cull/death rate averaging 37% over the previous 12 months. To the right of each listed parameter is a target value and a range (corresponding to the values given in Tables 1(a) & 1(b). In Figure 23 above the TARGET value for cull/death rate is 23% with a range of ±11%. These values are also displayed graphically to the left of the parameter titles. The target value is represented by the vertical black line. The area to the right hand side is shaded green to denote a performance level that is better than the target value. Left of the target line is shaded red denoting performance that is worse than the target value. The vertical red line represents the level that is “worse than the target by the range value” (so the performance of the poorer performing 25% of herds). In Figure 23 for culling rate, the red vertical line represents the target (23%) worse by the range (11%) so a culling rate of 34%. The positions of the black square and blue arrow show how the current herd is performing for each parameter relative to the specified target and range values. The arrow indicates any direction of change.

• The black square is the 12 month rolling average value for that parameter. So it is the longer-term performance based on the last 12 months of data (the value displayed to the left of the parameter title).

• The blue arrow head is the 3 months rolling average value for that parameter. In other words it is the short-term performance based on the last 3 months only. The line and arrow show the difference and direction of change between the 3 and 12 month average values. Beware that while this may indicate a significant change in herd performance, the blue line may also be influenced by seasonal factors in that 3 month period.

Worse than target by the range value

Target value

Target value This

herd’ 12 months

Range

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Using the target and range values to highlight a herd’s strengths & weaknesses Herd strengths: This study identifies the level achieved by the best 25% of the herds for each parameter. That value is then set as the “TARGET” for comparison with other herds. In Figure 22, any KPI with a black square to the right (green side) of the vertical black target line is “in the best 25%” when compared to the 500 study herds. In Figure 24 below, the herd displayed has 7 parameters that are “better than target” so this herd would currently be in the top 25% of herds nationally for those parameters. This mainly includes few 3 fertility parameters, in addition to some SCC parameters. Herd weaknesses: The vertical red line represents the performance achieved or bettered by 75% of the 500 herds (the target, worse by the range). Any parameter with a black square to the left of the vertical red line would be “in the bottom 25%” for that parameter when compared to the 500 study herds. There are 8 parameters highlighted in Figure 24, including longevity and milk yield (including protein and fat), so this herd would currently appear in the bottom 25% of herds for those parameters. Average performance levels: Parameters that fall between the vertical black and red lines are within the inter-quartile range (so the middle 50% of herds) when compared with the 500 study herds. Figure 24. Highlighting the strengths and weaknesses of a dairy herd

Figure 24 must be treated as a DISCUSSION DOCUMENT. The emphasis is on achieving an appropriate balance of performance in production, fertility and health. A parameter in the top 25% is

“Top 25%” performance

Lowest 25%

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not necessarily a good thing. The aim is to stimulate informed discussion between farmers and their advisers about what is happening and WHY.

Relationship between parameters: Herd SCC vs % chronic high SCC milk samples The 500 herd studies also provide data to investigate correlations between different Key Performance Indicators which can provide simple messages for farmers and advisers. A good example of this is the strong correlation between the Herd SCC and the percentage of milk samples deriving from chronic high SCC cows (2nd/3rd/4th etc consecutive high SCC milk sample). Figure 25 shows the distribution of the 500 herds from the current study (year ending 31st August 2020). Each blue square represents one of the 500 study herds. The very strong correlation (R2=0.752) is clearly evident giving a very clear message. If you have a high level of chronic cows in your herd you are also very likely to have a high herd SCC with all the costs and penalties associated with that. Figure 25. The relationship between herd average SCC and the % chronic high SCC cows

In addition to the correlation the graph shows that in herds where over 15% of the milk is from chronic cows the vast majority are penalised for having a high herd SCC. In 2020 there were 52 herds of this type and 47 (90%) of them also had a high herd SCC (averaging greater than 200,000 cells/ml). In contrast, there were 325 herds with less than 10% chronic cows of which only 35 (11%) also had a high herd SCC. This strong correlation has been evident in all the 11 annual KPI studies. Table 3 shows the enormous gains that the UK dairy industry has made in tackling high herd SCCs. The 65% of the herds (325/500) in the most recent study that qualify as “Low levels of chronic cows” (less than 10% chronic cows), are a dramatic improvement on the 24% of herds in the original study in 2010. Over the same time interval the % of herds keeping high levels of chronic cows (≥15% of the herd) has dropped from 41% of herds in 2010 to just 10% in 2020.

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Table 3. Percentage of herds with low (<10%) and high (≥15%) levels of chronic high SCC samples, in the KPI studies from 2010 to 2020

KPI study year Low levels of chronic cows

(<10% of milking cows) High levels of chronic cows

(≥15% of milking cows) 2010 24% of herds 41% of herds 2011 32% of herds 35% of herds 2012 34% of herds 30% of herds 2013 36% of herds 29% of herds 2014 42% of herds 24% of herds 2015 44% of herds 21% of herds 2016 51% of herds 18% of herds 2017 51% of herds 17% of herds 2018 56% of herds 12% of herds 2019 62% of herds 13% of herds 2020 65% of herds 10% of herds

In contrast to the strong correlation between herd SCC and the level of chronic cows, there is no clear correlation between the level of mastitis incidence and the herd SCC. Figure 26 shows the poor correlation observed in 2020. Similar poor correlation is observed in previous studies. Figure 26. The relationship between herd average SCC and mastitis incidence

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Appendix 1. Changes in Key Performance Indicators between 2010 and 2020 in herds included in every study over 11 years Since the initial study in 2010, wherever possible the same herds are kept in the sample used each year. If necessary, herds with poorly recorded fertility data and herds no longer recording were replaced with randomly selected new herds. Within the sample of the 2020 study, there remain 141 herds that have been included in all the 11 studies (2010 to 2020). As a check to confirm that replacement of some herds and retention of others has not introduced any unexpected bias in the sample, the table below shows the changes observed in KPIs over 11 years (2010 vs. 2020) for the ‘changing sample’ of 500 each year alongside the changes seen in the 141 herds common to all 11 years. The table shows similar trends in the ‘common 141’ herds to the trends on the ‘whole 500’ herd samples. Overall, these results do not suggest that significant bias has been introduced by the year-on-year partial replacement of herds in the sample.

500 herds groups 141 common herds

Median value Median value

Parameter Year of the study 2010 2020 2010 2020 A. Culling rate 24% 28% 24% 28% B. Culling / death rate in first 100 days of lactation 7% 5% 6% 5% C. Age at exit (years) 6.6 6.0 6.6 6.0 D. Age at exit by Lactations 3.9 3.5 4.0 3.5 E. Percentage Served by day 80 46% 60% 46% 62% F. Percentage conceived 100 days after calving 26% 36% 27% 35% G. Calving to 1st service interval (days) 105 80 102 77 H. Calving interval (days) 424 400 422 400 I. Age at 1st calving (years) 2.4 2.3 2.4 2.3 J. Conception rate 32% 35% 31% 35% K. Percentage service intervals at 18-24 days 30% 39% 32% 38% L. Percentage service intervals >50 days 32% 21% 29% 20% M. Percentage eligible for service that served 27% 40% 30% 41% N. Percentage eligible for service that conceived 9% 14% 10% 14% O. Lifetime milk / cow / day (kg) 10.5 12.8 11.6 12.4 P. Milk / cow / year (kg) 7,665 8,904 8,213 8,865 Q. Average Protein% 3.27% 3.32% 3.26% 3.33% R. Average Fat% 3.96% 4.13% 3.95% 4.09% V. Average SCC (‘000 cells/ml) 210 173 191 176 W. Percentage SCC >=200,000 cells/ml 24% 17% 22% 18% X. Percentage SCC >500,000 cells/ml 9% 7% 8% 7% Y. Percentage 1st recording SCC >=200,000 cells/ml 20% 16% 18% 17% Z. Percentage chronic SCC >=200,000 cells/ml 14% 8% 12% 9% ZA. Percentage Dry period cure (High:Low) 74% 76% 76% 75% ZB. Percentage Dry period protection (Low:Low) 84% 85% 85% 85% ZC. Percentage Low SCC at end of previous lactation 60% 76% 64% 76%

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Appendix 2. Key Performance Indicators definitions In the following definitions the average population of cows is calculated using animal days. Every day that animal is present in the population at risk during the period of study is a 365th of an animal year. The total animal days is divided by 365 to give animal years, which equates to the average population at risk. Parameter Description A. Culling rate The number of cows dying or culled during the 12 month period

expressed as a percentage of the average cow population for the same 12 month period.

B. Percentage culled / died 100 days after calving

The percentage of heifers/cows calving during the 12 month period that exit within 100 days after calving.

C. Age at exit (years) The average age (in days) of cows culled/died in the analysis period, divided by 365.24

D. Age at exit by lactations The average number of lactations completed by cows culled/died in the analysis period.

E. Percentage Served by day 80 The percentage of cows reaching the 80th day after calving that have been served at least once.

F. Percentage conceived 100 days after calving

The percentage of cows reaching 100 days after calving that have conceived.

G. Calving to 1st service interval (days)

The average days between calving and 1st service for all cows served for the first time in a lactation during the analysis period.

H. Calving interval (days) The interval between calvings, in days, for all re-calvings recorded in the analysis period.

I. Age at 1st calving (years) The age at first calving for all cows calving for the first time during the analysis period.

J. Conception rate The number of conceptions as a percentage of the total number of services (services to cows culled are included) during the analysis period.

K. Percentage service intervals at 18-24 days (Heat detection)

The percentage of all service intervals for cows returning to service during the analysis period that are between 18 and 24 days (equating to one oestrous cycle after the previous service).

L. Percentage service intervals >50 days

The percentage of all service intervals for cows returning to service during the analysis period that are over 50 days.

M. Percentage of cows eligible for service that were served (Submission rate)

The percentage of cows that are eligible for service (42 days+ after calving and not barren or already pregnant) during the analysis period that are served per 21 day (oestrous cycle) period.

N. Percentage of cows eligible for service that conceived (Pregnancy rate)

The percentage of cows that are eligible for service (42 days+ after calving and not barren or already pregnant) during the analysis period that conceive per 21 day (oestrous cycle) period.

O. Lifetime milk / cow/day (kg) The total milk produced per cow and heifer place in the year. The total milk produced in the year, divided by the average population of cows (both in milk and dry) and heifers (including heifer replacements being reared elsewhere), divided by 365.

P. Milk / cow / year (kg) The total milk produced per cow place in the year. The total milk divided by the average population of cows (both in milk and dry).

Q. Average protein% The weighted average protein% of all milk recorded during the analysis period.

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Parameter Description R. Average fat% The weighted average fat% of all milk recorded during the

analysis period. S. 305 day yield (kg) The average 305 day production for all cows reaching 305 days

after calving during the analysis period. T. 305 day protein (kg) The average 305 day production of milk protein for all cows

reaching 305 days after calving during the analysis period. U. 305 day fat (kg) The average 305 day production of milk fat for all cows reaching

305 days after calving during the analysis period. V. Average SCC (‘000 cells/ml) The weighted average somatic cell count of all milk recorded

during the analysis period. W. Percentage SCC ≥200,000 cells/ml

The percentage of all recorded milk samples during the analysis period that had an individual SCC reading of 200,000 cells/ml or higher.

X. Percentage SCC ≥500,000 cells/ml

The percentage of all recorded milk samples during the analysis period that had an individual SCC reading of 500,000 cells/ml or higher.

Y. Percentage 1st recording SCC ≥200,000 cells/ml

The percentage of all cows starting new lactations that had a high SCC (≥200,000 cells/ml) reading at the first milk recording in the lactation.

Z. Percentage chronic SCC ≥200,000 cells/ml

The percentage of all milk samples taken in the analysis period that originated from chronic SCC cows where the current and previous milk samples both had SCC levels of 200,000 cells/ml milk or greater.

ZA. Percentage Dry period cure (High:Low)

Of re-calving cows recorded starting a new lactation during the analysis period: the percentage of cows ending the previous lactation with a HIGH SCC (≥200,000 cells/ml) that started the new lactation with a LOW SCC (<200,000 cells/ml).

ZB. Percentage Dry period protection (Low:Low)

Of re-calving cows recorded starting a new lactation during the analysis period: the percentage of cows ending the previous lactation with a LOW SCC (<200,000 cells/ml) that also started the new lactation with a LOW SCC (<200,000 cells/ml).

ZC. Percentage Low at end of previous lactation (SCC<200,000 cells/ml)

Of re-calving cows recorded starting a new lactation during the analysis period: The percentage that had a LOW SCC (<200,000 cells/ml) at the last milk recording in the previous lactation.

ZD. Percentage New SCC ≥200,000 cells/ml

The percentage of all recorded milk samples that were of the “New” SCC Category, namely the first HIGH SCC (≥200,000) in a lactation following one or more low SCC samples.

ZE. Percentage Dried-off with no SCC ≥200,000 cells/ml

The percentage of cows completing a lactation without recording a high SCC (cows recording only LOW SCC samples (<200,000 cells/ml) in the previous lactation).

ZF. Threshold Index new high / new low

Of cows with consecutive milk records in the same lactation, the number of cows changing from Low SCC at the previous to High SCC at the next recording divided by the number of cows going from High SCC at the previous to Low SCC at the next recording.

ZG. Recovery percentage of new/first/repeat infections

Of HIGH SCC cows (≥200,000cells/ml) that at the previous recording were either low SCC or not yet in milk, the percentage that were LOW SCC (<200,000 cells/ml) at the following recording.

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Parameter Description ZH. Recovery percentage of chronic infections

Of CHRONIC High SCC cows (High SCC cows that at the previous recording were also High SCC), the percentage of those milked that were LOW SCC (<200,000 cells/ml) at the following recording.

ZI. Percentage drying off with no mastitis cases

The percentage of cows completing a lactation without recording a mastitis case.

ZJ. Mastitis rate (cases/100 cows in milk per year)

The total cow cases of mastitis recorded divided by the average population of cows in milk, represented as a % (cases/100 cows in milk).

ZK. Index mastitis case by Day 30

The percentage of cows calving during the12 month period that recorded a mastitis case by day 30 of the lactation.

ZL. Index mastitis rate after Day 30

The incidence rate of index mastitis cases in cows that have passed 30 days since calving.

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Appendix 3. Herd Companion High SCC Categories The web-based Herd Companion program (www.nmr.co.uk/Herd-companion) was introduced by NMR in 2003 primarily to support the use of milk recording data to control somatic cell counts (SCC) in dairy herds. Herd Companion focuses more on the duration of a high SCC infection rather than the magnitude of an individual milk sample. Using a threshold of 200,000 cells/ml milk to indicate infection, the program aims to balance the ability of many cows to self-cure with the need to assist cows where infection is becoming established. While in the region of 50% of cows self-cure after an initial raised SCC this recovery rate falls to less than 20% once a cow has recorded a second high SCC. It is these persistent high SCC cows that require attention before they are damaged irretrievably by a sustained period of infection. The development of Herd Companion led to the definition of four main categories of high cell count cow, as illustrated below. Each vertical bar represents the magnitude of the SCC at each milk recording in a lactation. Where the bar is black the SCC is below the threshold of 200,000 cells/ml milk. A red bar indicates a SCC level above the threshold.

NEW: The “New” category describes cows recording their first high SCC in the lactation, having recorded one or more low SCCs at earlier recording(s). An infection acquired in the lactation. FIRST: The “First” category describes cows that are HIGH SCC at their First milk recording in the current lactation. This is an infection that may be related to the dry period. REPEAT: The “Repeat” category describes a possible re-infection (or failure to cure). A cow that had high SCC recording(s) earlier in the current lactation recorded a LOW SCC in the previous month(s) but has returned to a High SCC at the latest recording. Chronic: The “Chronic” category describes a cow that is High SCC at the latest recording AND was also High SCC at the PREVIOUS recording(s). So she was high SCC last time and failed to recover. In the example above the cow has 7 consecutive high SCC recordings so has been defined as Chronic for the last 6 months of consecutive high SCC recordings.

http://www.nmr.co.uk/Herd-companion

key performance indicators for the uk national dairy herd

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